[erlang-questions] ets table disappears after bad query

[Gleb Peregud]

Ets table is always linked to some process. When the owner process of a
table dies, the table is destroyed. In your case it is linked to shell
process. By default shell process dies if any exception happens in the code
it runs.

BR,
Gleb Peregud
On 2 May 2011 07:55, "Todd" <t.greenwoodgeer@REDACTED> wrote:
> I have an ets query that is broken. The funny thing is that after the
> query fails, the ets table disappears...
>
> Here's the code...mostly ripped off from the file doc entry:
> git://gist.github.com/951214.git
>
> REPRO:
>
> 1. the ets table does not exist
>
> 127> ets:all().
> [8207,4110,13,file_io_servers,inet_hosts_file_byaddr,
> inet_hosts_file_byname,inet_hosts_byaddr,inet_hosts_byname,
> inet_cache,inet_db,global_pid_ids,global_pid_names,
> global_names_ext,global_names,global_locks,ac_tab]
> 128>
>
> 2. running the test creates the ets table, 'file_test'
>
> dynamic_file:test().
>
> -----------------------------------------
> create_file_slow
> -----------------------------------------
> create_file_slow,4884,1024,0.20966420966420968,1,
> create_file_slow,16569,2048,0.1236043213229525,1,
> create_file_slow,41857,4096,0.09785698927300093,1,
> create_file_slow,135915,8192,0.060272964720597434,1,
> create_file_slow,564260,16384,0.029036259880197073,1,
> create_file_slow,525989,32768,0.062297880754160255,1,
> -----------------------------------------
> create_file (fast)
> -----------------------------------------
> create_file,13306,1024,0.07695776341500075,1,
> create_file,2907,1024,0.3522531819745442,2,
> create_file,1435,1024,0.713588850174216,4,
> create_file,740,1024,1.3837837837837839,8,
> ...
> create_file,468,1024,2.1880341880341883,16,
> create_file,3132,32768,10.462324393358877,2048,
> create_file,3556,32768,9.214848143982003,4096,
> ok
>
> 3. verify the ets entry exists (it does)
>
> 129> ets:all().
> [file_test,8207,4110,13,file_io_servers,
> inet_hosts_file_byaddr,inet_hosts_file_byname,
> inet_hosts_byaddr,inet_hosts_byname,inet_cache,inet_db,
> global_pid_ids,global_pid_names,global_names_ext,
> global_names,global_locks,ac_tab]
>
>
> 4. run my broken query. i'm trying to sort the results by a specific
> column so that I can find what block size results in the best
> performance...not sure yet what's wrong with the query, but i'll figure
> it out:
>
> 130> lists:sort(fun({_,_,_,A,_}, {_,_,_,B,_}) -> A < B end,
> ets:match(file_test, {create_file, '$0', '$1', '$2', '$3'})).
> ** exception error: no function clause matching
> erl_eval:'-inside-an-interpreted-fun-'([13306,1024,0.07695776341500075,1],
> [2907,1024,0.3522531819745442,2])
>
> 5. look at the ets tables again, and whoa, the 'file_test' table is gone!
>
> 131>
> ets:all().
>
> [8207,4110,13,file_io_servers,inet_hosts_file_byaddr,
> inet_hosts_file_byname,inet_hosts_byaddr,inet_hosts_byname,
> inet_cache,inet_db,global_pid_ids,global_pid_names,
> global_names_ext,global_names,global_locks,ac_tab]
>
> 6. Is this expected behaviour? What would I have to do to prevent losing
> my ets table?
>
> -Todd
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